Typical cone crusher comprises a truncated conical crushing bowl, whose wall supports a fixed crushing blade, and a conical head bearing the inner crushing blade mounted on a shaft coaxial to the bowl. The geometrical axis of the conical head forms at the summit of the latter a certain angle with the axis of the principal shaft, which gives a nutatory movement to the head when the eccentric turns. During descent into the bowl, the materials are progressively crushed so as to reach the dimension of the smallest space between the fixed crushing blade and the inner crushing blade.
The inner crushing blade is mounted on the head and rests in its lower portion on the head, whilst it is fastened at its upper portion on the head by a screw, by means of a ring. This gripping is effected by a component of the gripping force of the screw directed along the generatrix of the cone of the inner crushing blade.
In the course of the crushing operation, the pieces which wear down most quickly are the crushing blades and particularly this inner crushing blade. Because of this, the inner crushing blade must be periodically changed due to wear.
To this end, it is fixed immovably on the head by means of the screw. This fastening of the screw requires a very high force so as to avoid the crushing blade knocking against the head. To fasten the blade, a key is generally used on which the operator taps with a sledgehammer. Moreover, in the course of operation, the inner crushing blade has the tendency to turn on the head but, with this movement, it drives the screw which self-locks while holding the crushing blade. The self locking of the screw ensures that disassembly also requires the application of a very high force. To facilitate disassembly, a ring is interposed, e.g. welded, between the screw head and the upper edge of the inner crushing blade. For disassembly, this ring is cut with a blowtorch and removed with a suitable tool, which frees the screw but which can then turn freely.
The prior art discloses also such solution where hydraulic power is applied in order to fasten the inner crushing blade on to the head of a crusher. In document FR 2298368 it is disclosed a cone crusher wherein the component forcing the inner crushing blade is moved towards the head by pressing it from its upper part by means of hydraulic cylinder. However, in this device the rotation of the piston in to which said component is attached has not been restrained and thus this device has disadvantage that it does not prevent the rotation of the inner crushing blade in respect of the head. An another drawback concerning to this solution is that this kind of fastening device requires that the adjusted pressure in the cylinder has to be maintained continuously since there is no other means in this type of device for keeping the said component in the position in which it fixes the inner crushing blade on to the head of the crusher.
Strong fastening is necessary to prevent the crushing blade from turning relative to the fastening screw head. There is a need for a sophisticated fastening solution than present solutions.